System and method for determining and adjusting fuel injection control parameters

ABSTRACT

A method of controlling an engine system includes controlling a fuel injector to perform a zero-fueling injector operation during operation of the engine, the zero-fueling injector operation including a non-zero injector on-time resulting in zero fueling by the injector, determining an injection system pressure change associated with the zero-fueling injector operation, modifying at least one fuel injection control parameter in response to the injection system pressure change, and using the modified fuel injection control parameter to control injection of fuel by the fuel injector during operation of the engine.

CROSS-REFERENCE

The present application claims the benefit of and priority to U.S.Application Ser. No. 62/720,351 filed Aug. 21, 2018, the disclosure ofwhich is hereby incorporated by reference.

BACKGROUND

The present application relates to apparatuses, methods, systems, andtechniques for determining and adjusting fuel injection controlparameters and controlling fuel injection during engine operation. Undersome operating conditions, engines benefit from delivering very smallquantity injection pulses in order to improve fuel economy, improveengine performance, reduce audible noise, and improve emission. It wouldbe desirable to provide a robust technique to accurately and preciselydetermine or estimate and deliver very small injection pulses for eachindividual injector in an injection system, under any operatingconditions, and throughout the lifetime of the engine system. In orderto control fuel injection to such a degree of accuracy and precision, itis necessary to know the injector commanded on-time associated with aninjection quantity at any operating pressure. A number of proposals havebeen made to determine or estimate these minimum parameters. Butconventional approaches suffer from a number of drawbacks, limitations,shortcomings and undesirable results including, for example, theoccurrence of injection at undesired times, parasitic drag on fueleconomy, increased noise, vibration and harshness, and increases inundesirable emissions. There remains a substantial need for the uniqueapparatuses, methods, systems, and techniques disclosed herein.

DISCLOSURE OF ILLUSTRATIVE EMBODIMENTS

For the purposes of clearly, concisely and exactly describingillustrative embodiments of the present disclosure, the manner, andprocess of making and using the same, and to enable the practice, makingand use of the same, reference will now be made to certain exemplaryembodiments, including those illustrated in the figures, and specificlanguage will be used to describe the same. It shall nevertheless beunderstood that no limitation of the scope of the invention is therebycreated and that the invention includes and protects such alterations,modifications, and further applications of the exemplary embodiments aswould occur to one skilled in the art.

SUMMARY OF THE DISCLOSURE

Exemplary embodiments include unique apparatus, methods, systems andtechniques for determining and adjusting fuel injection controlparameters and controlling fuel injection during engine operation.Further embodiments, forms, objects, features, advantages, aspects, andbenefits shall become apparent from the following description anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of certain aspects of an exemplaryengine system.

FIG. 2 is a schematic illustration of certain aspects of an exemplaryoff-engine fuel injector test system.

FIG. 3 is a flow diagram illustrating certain aspects of an exemplaryfuel injection control process which may be performed in an enginesystem.

FIG. 4 is a block diagram illustrating certain aspects of an exemplaryfuel injection controls which may be provided in an engine system.

FIGS. 5-10 are graphs illustrating a number of exemplary measurement anddetermination principles and techniques which may be utilized inconnection with fuel injection control processes such as the exemplaryprocess of FIG. 3.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

With reference to FIG. 1, there is illustrated a schematic depiction ofcertain aspects of an exemplary engine system including an internalcombustion engine 10. In the illustrated embodiment engine 10 is adirect injection diesel engine. In other embodiments, the engine may beanother type of engine which includes one or more fuel injectors, suchas a dual-fuel engine, or other types of engines which include one ormore fuel injectors. Engine 10 includes an engine body 11, whichincludes an engine block 12 and a cylinder head 14 attached to engineblock 12, a fuel system 16, and a control system 18. Control system 18receives operational inputs or signals from sensors located on engine 10and transmits control signals to devices located on engine 10 to controlthe function of those devices, such as one or more fuel injectors.

Control system 18 can be configured to perform on-engine operations andprocesses which are performed during engine operation, such as theoperations and processes described herein. Such on-engine operations andprocesses may be performed to adjust fuel injection control parameters.One example of a fuel injection control parameter is the maximuminjector on-time which will produce zero fueling (T_(zf)) at a giveninjection system pressure. The value of T_(zf) under a given set ofoperating conditions can serve as a foundational combustion controlreference parameter from which injector-on times that provide a desiredand commanded quantity of fuel injection corresponding to a desired andcommanded engine torque output can be determined. Thus, for a giveninjection pressure, fuel injection timing commands which cause injectorsassociated with engine 10 to fuel the engine may be based upon ordetermined in response to the value of T_(zf) under a given set ofoperating conditions.

Engine body 12 includes a crankshaft 20, a plurality of pistons 22, 24,26, 28, 30, and 32, and a plurality of connecting rods 34. Pistons 22,24, 26, 28, 30, and 32 are positioned for reciprocal movement in aplurality of engine cylinders 36, with one piston positioned in eachengine cylinder 36. One connecting rod 34 connects each piston tocrankshaft 20. As will be seen, the movement of the pistons under theaction of a combustion process in engine 10 causes connecting rods 34 tomove crankshaft 20. While engine 10 is shown having six cylinders,engine 10 may include any number of cylinders from a single cylinder tomultiple cylinders. In the exemplary embodiment, engine 10 includes sixcylinders arranged in an inline configuration. However, engine 10 mayinclude any number of cylinders, such as one, two, four, six, twelve,etc., arranged in a variety of configurations, including inline,straight, flat, V and W configurations, to name several examples.

In an exemplary embodiment, a plurality of fuel injectors 38 ispositioned within cylinder head 14. Each fuel injector 38 includes oneor more injector orifices 66, shown schematically in FIG. 2, thatfluidly connect a respective fuel injector 38 to a combustion chamber40, each of which is formed by one piston, cylinder head 14, and theportion of engine cylinder 36 that extends between the piston andcylinder head 14.

Fuel system 16 provides fuel to injectors 38, which is then injectedinto combustion chambers 40 by the action of fuel injectors 38. Fuelinjector 38 may include a nozzle valve or needle valve element (notshown) that moves from a closed position to an open position and thenfrom the open position to the closed position, providing an injectionevent. The nozzle or needle valve element may move from the closedposition to the open position when one or more of a solenoid, apiezoelectric actuator, or another actuator of fuel injector 38 isenergized by control system 18 to inject fuel through the injectororifices 66 into combustion chamber 40 during an injection event. Afterfuel injector 38 is energized, a drain fuel flow may flow from fuelinjector 38 into a drain fuel circuit portion 39, which returns thedrain fuel flow to a location where the drain fuel may be used by engine10, such as fuel tank 44. Because of the delay times between both thestart energization of the injector's pilot valve and the start of thedrain flow and the later start of injection as well as the delay timesfrom the start of de-energization to the end of the drain flow and theend of injection, the drain flow will continue even after the injectoris de-energized. The nozzle or needle valve element remains open for atime period, called the injection duration, that provides apredetermined volume, amount, or quantity of fuel to combustion chamber40, as determined by control system 18 based on operation state inputs,such as acceleration and torque or power. At the end of thepredetermined time period, control system 18 de-energizes fuel injector38, which causes the nozzle or needle valve element to close, ending theinjection event. While in this example, the nozzle or needle valveelement is described as opening when energized and closing whende-energized, fuel injector 38 may also operate in an opposite mannerwhere the nozzle or needle valve element opens when de-energized andcloses when energized. Fuel injector 38 may be any of a variety of typesof fuel injectors.

Fuel system 16 includes a fuel circuit 42, a fuel tank 44 containing afuel, a high-pressure fuel pump 46 positioned along fuel circuit 42downstream from fuel tank 44, and a fuel accumulator or rail 48positioned along fuel circuit 42 downstream from high-pressure fuel pump46. While fuel accumulator or rail 48 is shown as a single unit orelement in the exemplary embodiment, accumulator 48 may be distributedover a plurality of elements that contain high-pressure fuel. Theseelements may include fuel injector(s) 38, high-pressure fuel pump 46,and any lines, passages, tubes, hoses and the like that connecthigh-pressure fuel to the plurality of elements, and a separate fuelaccumulator 48 may thus be unnecessary. Fuel system 16 also includes aninlet metering valve 52 positioned along fuel circuit 42 upstream fromhigh-pressure fuel pump 46 and one or more outlet check valves 54positioned along fuel circuit 42 downstream from high-pressure fuel pump46 to permit one-way fuel flow from high-pressure fuel pump 46 to fuelaccumulator 48. Fuel circuit 42 connects fuel accumulator 48 to fuelinjectors 38, which receive fuel from fuel circuit 42 and then providecontrolled amounts of fuel to combustion chambers 40. Fuel system 16 mayalso include a low-pressure fuel pump 50 positioned along fuel circuit42 between fuel tank 44 and high-pressure fuel pump 46. Low-pressurefuel pump 50 increases the fuel pressure to a first pressure level priorto fuel flowing into high-pressure fuel pump 46, which increases theefficiency of operation of high-pressure fuel pump 46.

Control system 18 may include a control module 56 and a wire harness 58.A number aspects of the disclosure are described in terms of sequencesof actions to be performed by elements of a computer system, controlsystem or other hardware capable of executing programmed instructions,for example, a general-purpose computer, special purpose computer,workstation, or other programmable data process apparatus. It will berecognized that in each of the embodiments, the various actions could beperformed by specialized circuits (e.g., discrete logic gatesinterconnected to perform a specialized function), by programinstructions (software), such as program modules, being executed by oneor more processors (e.g., one or more microprocessors, a centralprocessing unit (CPU), and/or application specific integrated circuit),or by a combination of both. For example, embodiments can be implementedin hardware, software, firmware, microcode, or any combination thereof.The instructions can be program code or code segments that performnecessary tasks and can be stored in a non-transitory machine-readablemedium such as a storage medium or other storage(s). A code segment mayrepresent a procedure, a function, a subprogram, a program, a routine, asubroutine, a module, a software package, a class, or any combination ofinstructions, data structures, or program statements. A code segment maybe coupled to another code segment or a hardware circuit by passingand/or receiving information, data, arguments, parameters, or memorycontents.

The non-transitory machine-readable medium can additionally beconsidered to be embodied within any tangible form of computer-readablecarrier, such as solid-state memory, magnetic disk, and optical diskcontaining an appropriate set of computer-executable instructions thatcause a processor to carry out the techniques described herein. Acomputer-readable medium may include the following: an electricalconnection having one or more wires, magnetic disk storage, magneticcassettes, magnetic tape or other magnetic storage devices, a portablecomputer diskette, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (e.g., EPROM, EEPROM,or Flash memory), or any other tangible medium capable of storinginformation.

Control system 18 may also include an injection system pressure sensor60 and a crank angle sensor. In the illustrated embodiment, injectionsystem pressure sensor 60 is provided as an accumulator or rail pressuresensor. It shall be appreciated that injection system pressure sensormay any of a number of types of pressure sensing devices including, forexample, pressure sensors configured to sense pressure at other fuelinjector system locations and may comprise a variety of pressure sensingsuch as a diaphragm, a force transducer, a strain gauge, or other typesof pressure sensing devices. The crank angle sensor may be a toothedwheel sensor 62, a rotary Hall sensor 64, or another type of devicecapable of measuring the rotational angle of crankshaft 20. Controlsystem 18 uses signals received from accumulator pressure sensor 60 andthe crank angle sensor to determine the combustion chamber receivingfuel, which may then be used to analyze the signals received fromaccumulator pressure sensor 60.

Control module 56 may be an electronic controller or control unit orelectronic control module (ECM) that may monitor conditions of engine 10or an associated vehicle in which engine 10 may be located. Controlmodule 56 may be a single processor, a distributed processor, anelectronic equivalent of a processor, or any combination of theaforementioned elements, as well as software, electronic storage, fixedlookup tables and the like. Control module 56 may include a digital oranalog circuit. Control module 56 may connect to certain components ofengine 10 by wire harness 58, though such connection may be by othermeans, including a wireless system. For example, control module 56 mayconnect to and provide control signals to inlet metering valve 52 and tofuel injectors 38.

When engine 10 is operating, combustion in combustion chambers 40 causesthe movement of pistons 22, 24, 26, 28, 30, and 32. The movement ofpistons 22, 24, 26, 28, 30, and 32 causes movement of connecting rods34, which are drivingly connected to crankshaft 20, and movement ofconnecting rods 34 causes rotary movement of crankshaft 20. The angle ofrotation of crankshaft 20 is measured by engine 10 to aid in timing ofcombustion events in engine 10 and for other purposes. The angle ofrotation of crankshaft 20 may be measured in a plurality of locations,including a main crank pulley (not shown), an engine flywheel (notshown), an engine camshaft (not shown), or on the camshaft itself.Measurement of crankshaft 20 rotation angle may be made with toothedwheel sensor 62, rotary Hall sensor 64, and by other techniques. Asignal representing the angle of rotation of crankshaft 20, also calledthe crank angle, is transmitted from toothed wheel sensor 62, rotaryHall sensor 64, or another device to control system 18.

Crankshaft 20 drives high-pressure fuel pump 46 and low-pressure fuelpump 50. The action of low-pressure fuel pump 50 pulls fuel from fueltank 44 and moves the fuel along fuel circuit 42 toward inlet meteringvalve 52. From inlet metering valve 52, fuel flows downstream along fuelcircuit 42 to high-pressure fuel pump 46. High-pressure fuel pump 46moves the fuel downstream along fuel circuit 42 through outlet checkvalves 54 toward fuel accumulator or rail 48. Inlet metering valve 52receives control signals from control system 18 and is operable to blockfuel flow to high-pressure fuel pump 46. Inlet metering valve 52 may bea proportional valve or may be an on-off valve that is capable of beingrapidly modulated between an open and a closed position to adjust theamount of fluid flowing through the valve.

Fuel pressure sensor 60 is connected with fuel accumulator 48 and iscapable of detecting or measuring the fuel pressure in fuel accumulator48. Fuel pressure sensor 60 sends signals indicative of the fuelpressure in fuel accumulator 48 to control system 18. Fuel accumulator48 is connected to each fuel injector 38. Control system 18 generatesand transmits or provides injection control signals to fuel injectors 38that determine operating parameters for each fuel injector 38. Suchinjection control signals may include the length of time fuel injectors38 operate or are actuated, also called the on-time. The commandedon-time to injector 38 is the length of time for which actuator portion78 is energized. The duration of the opening of electrically actuatedvalve portion 74 is controlled by adjusting the commanded on-time. Ifthe resulting duration of the opening of the valve portion 74 for theindividual injector at the operating conditions is sufficiently longthen the valve plunger (not shown) will respond by opening which willresult in injection flow through the injector orifices 66 to combustionchamber 40. The injection control signals may also include the rate atwhich the nozzle valve element opens and closes, and timing of theopening and closing of the nozzle valve element with respect to theangle of crankshaft 20. Thus, the injection control signals control theamount of fuel delivered by each fuel injector 38 and the timing of fueldelivery with respect to a position of a piston in a respective cylinder36.

Referring to FIG. 2, in an exemplary embodiment fuel injector 38includes a valve portion 68 for providing fuel by way of fuel injectororifice(s) 66 to combustion chambers 40. Fuel injector 38 also includesa fluid inlet 70, and a drain outlet 72. Valve portion 68 is positionedbetween fluid inlet 70 and injector orifice(s) 66, and between fluidinlet 70 and drain outlet 72. Valve portion 68 may include anelectrically actuated valve portion 74 and a pilot actuated portion 76.Pilot actuated portion 76 of valve portion 68 is positioned betweenfluid inlet 70 and injector orifice(s) 66. Electrically actuated valveportion 74 is positioned between pilot actuated portion 76 and drainoutlet 72. Electrically actuated valve portion 74 is connected to acontrol system, such as control system 18 or a test control system 108,and receives signals from the control system to cause electricallyactuated valve portion 74 to operate.

Electrically actuated valve portion 74 includes an actuator portion 78and a bias spring 80. Electrically actuated valve portion 74 may be in avariety of configurations, including normally open and normally closed,depending on the configuration of actuator portion 78. In the exemplaryembodiment, electrically actuated valve portion 74 is normally closed,maintained by bias spring 80, which prevents fuel flow from pilotactuated portion 76 to drain outlet 72. Pilot actuated portion 76includes a bias spring 82 that keeps pilot actuated portion 76 biasedinto a closed position. Actuator portion 78 may be a solenoid, apiezoelectric actuator, or another type of actuator.

Fuel injector 38 operates by receiving an injection control signalgenerated by the control system. The injection control signal isreceived by electrically actuated valve portion 74, causing actuatorportion 78 to energize, moving a valve plunger (not shown) withinelectrically actuated valve portion 74 from the closed position shown inFIG. 2 to an open position, which permits a drain fluid to flow frompilot actuated valve portion 76 toward drain outlet 72. The drain fluidflows from a control chamber (not shown) in pilot actuated valve portion76, which permits pilot actuated valve portion 76 to move from theclosed position shown in FIG. 2 to an open position because of a netforce against pilot actuated valve portion 76. With pilot actuated valveportion 76 in an open position, fuel is able to flow from fluid inlet 70to injector orifice(s) 66. The configuration of fuel injector 38, andmore particularly valve portion 68, is just one embodiment of many thatare able to take advantage of the present disclosure. The principalcriterion for any valve embodiment is that drain flow needs to have adefinable and consistent relationship to the injected fuel quantity. Aslong as the relationship between drain flow and injected fuel quantitycan be established for a valve portion, then the valve portion iscompatible with the system and method of the present disclosure.

With continuing reference to FIG. 2, each fuel injector design or partnumber may be characterized in a test fixture shown as a simplifiedschematic and generally indicated at 100. Test fixture 100 may be usedto predefine a fuel quantity relationship between the amount of fluidflowing through a drain of fuel injector 38 and the amount of fluiddelivered through one or more injector orifice(s) 66. Once thisrelationship is defined for a particular fuel injector design, which maybe associated with a part number, then dimensional and configurationcontrols may be established to define this relationship, which appliesto future fuel injectors produced to the same design. Even thoughindividual fuel injectors need not be tested once a design is qualified,a test fixture similar to test fixture 100 may obtain a limited numberof data points for either a sample of fuel injectors or each fuelinjector to ensure each fuel injector is operating in accordance withthe predefined relationship. Thus, test fixture 100 provides acorrelation or fuel quantity relationship between an amount or quantityof drain fuel flow and an amount or quantity of injected fuel flow forthe defined fuel injector configuration for one or more operationalstates. Test fixture 100 includes appropriate mounting hardware (notshown) to secure each fuel injector 38 so that fluid and electricalconnections to fuel injector 38 may be made. Test fixture 100 includes afluid circuit 102, which further includes a drain fuel circuit portion104 and an injection circuit portion 106. Test fixture 100 also includesa pump 114, an accumulator 116, a reservoir 118, a relief valve 120,and, in the exemplary embodiment, a plurality of flow meters 122.

Fluid circuit 102 extends from reservoir 118. Pump 114 is positionedalong fluid circuit 102 downstream from reservoir 118. Pump 114 operatesto draw fluid from reservoir 118 and to move fluid through fluid circuit102. The fluid used in test fixture 100 may be a fuel such as diesel ormay be another test fluid with a viscosity similar to fuel, such as alubricant, complex hydrocarbon, coolant, or other fluid suitable forpumping under high pressure, e.g., greater than 1,000 bar. Accumulator116 is positioned along fluid circuit 102 downstream from pump 114. Aflow meter 122 c may be positioned along fluid circuit 102 downstreamfrom reservoir 116; however, flow meter 122 c is preferably omitted asthe flow quantity that it would measure may be determined as the sum ofthe flow through flow meters 122 a and 122 b. Fluid circuit 102 alsoincludes a relief circuit portion 124 that connects accumulator 116 withreservoir 118. Relief valve 120 is positioned along relief circuit 124between accumulator 116 and reservoir 118 and serves to limit themaximum pressure in the accumulator. The control system controls thepump delivery quantity to achieve and maintain the pressure in theaccumulator. A flow meter 122 a is positioned along drain fuel circuit104, which connects to reservoir 118. A flow meter 122 b is positionedalong injection circuit portion 106.

Test fixture 100 also includes test control system 108. Test controlsystem 108 may include a test control module 110 and a test wire harness112. Test control system 108 may send control signals to pump 114 and toa fuel injector 38 being tested and may receive drain flow quantity flowsignals from flow meter 122 a and injection flow quantity signals fromflow meter 122 b.

In order to characterize a fuel injector 38, fuel injector 38 ispositioned within test fixture 100. Fluid circuit 102 of test fixture100 is connected to fluid inlet 70 of fuel injector 38. Drain fuelcircuit portion 104 of test fixture 100 is connected to drain outlet 72of fuel injector 38. Injection circuit portion 106 of test fixture 100is connected to injector orifice(s) 66 of fuel injector 38. Test controlsystem 108 is connected to actuator portion 78 by way of wire harness112, which includes a suitable electrical connector for attaching to orinterfacing with electric actuation portion 78, though such connectionbetween test control system 108 and actuator portion 78 may be by othertechniques, including a wireless transmitter and receiver arrangement.Once fuel injector 38 is connected as described hereinabove, an operatorof test fixture 100 may now start a test process of fuel injector 38.

The test process consists of providing a signal from test control system108 to energize actuator portion 78. When actuator portion 78 isenergized, electrically actuated valve portion 74 opens, relieving fuelpressure from a control chamber (not shown) of pilot actuated valveportion 76 through drain fuel circuit portion 104, where the drain fluidflows into reservoir 118. As drain fluid flows through drain fuelcircuit portion 104, the flow rate or volume of drain flow may bemeasured by flow meter 122 a. Drain flow may be measured in other ways,such as by using mass meters, ultrasonic meters, or any other suitablemethod for measuring drain flow. The drain flow quantity may also beestimated using a simulation. The relief of pressure permitshigh-pressure fluid to move pilot actuated valve portion 76 to an openposition. As pilot actuated valve portion 76 opens, fluid flows fromfluid circuit 102 through pilot actuated valve portion 76 and then toinjector orifice(s) 66. From injector orifice(s) 66, the fluid flowsthrough flow meter 122 b and into reservoir 118. To close pilot actuatedvalve portion 76, actuator portion 78 may be de-energized, which blocksdrain flow from exiting fuel injector 38 through drain outlet 72.Pressure then builds in the control chamber (not shown), and a net forceagainst pilot actuated valve portion 76 forces pilot actuated valveportion 76 to a closed position.

The drain flow signals from flow meters 122 a and 122 b are sent to testcontrol system 108, which calculates the amount of fluid deliveredthrough injector orifice(s) 66 in relationship to the amount of fluidthat flows through drain fuel circuit portion 104. Test fixture 100 mayuse a variety of flow meter configurations. For example, there may be adifferent number and location of flow meters than shown in FIG. 2 toprovide the necessary data to find the fuel quantity relationshipbetween the amount or flow rate of drain fluid flow and the amount orflow rate of fuel flow through the injector orifice(s) 66 during aninjection event. A suitable flow meter configuration enables calculationof fluid flow into drain fuel circuit 104 and fluid flow into injectioncircuit portion 106. Because it only requires two flow meters to performthe required calculations, the positions of the flow meters shown inFIG. 2 should be considered as possible locations for the flow meters.

Engine systems, such as the example illustrated in and described inconnection with FIG. 1, and test systems, such as the exampleillustrated in and described in connection with FIG. 2, may be utilizedin connection with a process which determines or estimates a pilot valvedrain quantity (Q_(pvzf)) associated with the commanded injector on-time(T_(zf)) which corresponds to zero fueling injection quantity from themeasured pressure drop data. The process may utilize a modelingmethodology in determining or estimating Q_(pvzf) and T_(zf) thatincludes both off-engine calibration (performed in a test rig) andon-engine adaptation (performed during operation of the engine) ofQ_(pvzf) and T_(zf).

The off-engine calibration operations may be performed in connectionwith a test system such as the example illustrated and described abovein connection with FIG. 2. A first off-engine calibration operation canbe used to define nominal coefficients values for nominal T_(zf) andQ_(pvzf) equations. For example, the nominal commanded injector on-timeat which the injector begins to fuel (T_(zf)) and the nominal pilotvalve drain flow associated with that on-time (Q_(pvzf)) may bedetermined in accordance with equations (1) and (2):

$\begin{matrix}{\frac{1}{T_{zf}} = {C_{{Tzf}\; 0} + {C_{{Tzf}\; 1}P} + \frac{C_{{Tzf}\; 2}}{P}}} & (1) \\{Q_{pvzf} = {C_{{Qpv}\; \_ \; {nomina}\; {l\_}0} + {C_{{Qpv}\; \_ \; {nomina}\; {l\_}1}*P} + {C_{{Qpv}\; \_ \; {nominal}\; \_ 2}*P^{2}}}} & (2)\end{matrix}$

In equation (1) C_(Tzf0) C_(Tzf1), C_(Tzf2) are the nominal coefficientswhich are determined from rig testing. These coefficients adapton-engine for each injector based on estimated pilot valve drainquantity from pressure drop measurements and P is pressure. In equation(2) C_(Qpv_nominal_0), C_(Qpv_nominal_1), C_(Qpv_nominal_2) arecoefficients which are determined from rig testing and which, in certainforms, are not adapted during on-engine operation and P is pressure. Forexample, in equation 2 Qpvzf is Qpvzf_nominal. For the nominal injectorCQpv_nominal_0, CQpv_nominal_1, and CQpv_nominal_2 are not adaptedon-engine; however, there can be a relationship between T_(zf) and Pwhich adapts on-engine the value of Qpvzf as a function of Tzf and P foreach injector.

A second off-engine calibration operation can be used to define thecoefficients for the pilot valve drain flow only measurement target(Q_(pv drain only)) by subtracting out the quantity of fuel injected. Athird off-engine calibration operation can then be used to define thecoefficients/equation which define the pilot valve drain flow onlyquantity sensitivity to variation in injection system pressure andT_(zf). A fourth off-engine calibration operation can be used to definethe coefficients which define the sensitivity of changes in Q_(pvzf) ofan injector to changes in T_(zf) of an injector.

The on-engine adaptation of the pilot valve drain quantity valueQ_(pvzf) and the zero fueling injection on-time T_(zf) may be performedin connection with an operational engine system such as that illustratedand described above in connection with FIG. 1. For example, withreference to FIG. 3 there is illustrated a flow diagram depictingcertain aspects of an exemplary process 200 which may be implemented inand performed by an electronic control system associated with aninternal combustion engine powertrain such as control system 18. Process200 is one example of a process which may be performed to estimate anindividual injector's pilot valve drain quantity (Q_(pvzf)) associatedwith the commanded injector on-time which corresponds to zero fuelinginjection quantity (T_(zf)) from the measured pressure drop data. Thesevalues may be adapted from nominal starting values determined inoff-line calibration for a type or class of injectors.

Process 200 utilizes inputs indicative of both measured or estimatedoperating conditions and system characteristics determined throughoff-engine calibration. For example, input 202 provides the currentoperating pressure for the injector being tested. In the case ofcommon-rail systems, the rail pressure may be utilized as the currentoperating pressure for each injector that is tested. Other types ofsystems may utilize different measurements of current operatingpressure, such as injector-specific measurements. Input 202 is providedto input 204, and to operations 211 and 214 all of which can vary inresponse to variation in the current operating pressure for an injectortest. Input 204 provides the desired pilot valve drain flow margin atthe operating pressure below that expected to produce a non-zeroinjection event to operations 211 and 214.

Process 200 includes a control loop 210 including operations 211-216which may be executed in a repeating sequence during engine operation.Process 200 is preferably performed during events where no fueling iscommanded for torque generation, such as when a vehicle is coasting ormotoring downhill. However, process 200 if desired could take place atany time during the engine's operation since it results in no additionalfuel being injected in the combustion chamber. For example, an injectorcan be commanded to produce a drain only pulse or pulses at any timeduring the engines operation and the resulting magnitude of the drainonly pulse or pulses associated pressure drop can be obtained afteraccounting for pressure changes which resulted from all other sources.The operations of control loop 210 may be performed as a function ofboth the injector to be tested and the operating pressure to provide foradaptation injection control parameters particular to each injector inan injection over a board range of injection system operating pressures.

Operation 211 determines the commanded injector on-time at the currentoperating condition for the operating injector to produce the desiredpilot valve drain only pulses quantity. In certain forms, operation 211calculates the commanded injector on-time which is intended to produce adrain flow only injection event in accordance with equation (3):

$\begin{matrix}{T_{{Drain}\mspace{14mu} {Only}\mspace{14mu} {Measurement}\mspace{14mu} {Target}} = {T_{zf} - \frac{\left( {Q_{pvzf} - Q_{{Drain}\mspace{14mu} {Only}\mspace{14mu} {Measurement}\mspace{14mu} {Target}}} \right)}{\left( {C_{{{dQ}/{dT}}\; 0} + {C_{{{dQ}/{dT}}\; 1}P} + {C_{{{dQ}/{dT}}\; 2}/T_{zf}^{2}}} \right)}}} & (3)\end{matrix}$

Operation 212 commands injection in accordance with the value determinedfor T_(Drain Only Measurement Target). In certain forms, operation 212may command this operation for a single pulse. In certain formsoperation 212 may command this operation for multiple pilot valve drainonly pulses to a test injector. Further details of the use of multiplepilot valve drain only pulses to a test injector are illustrated in anddescribed in connection with FIGS. 9 and 10.

Operation 213 estimate the quantity of fuel per pulse which was removedfrom the high-pressure system using a method such as determining thisquantity from the high-pressure system pressure drop.

Operation 214 estimates the commanded injector on-time T_(zf) whichwould be at the threshold of producing an injection event at theoperating test conditions for the test injector. In certain forms,operation 214 estimate T_(zf) for the test in accordance with equation(4):

$\begin{matrix}{T_{zf} = {T_{{Commanded}\mspace{14mu} {Drain}\mspace{14mu} {Only}\mspace{14mu} {Measurement}\mspace{14mu} {Target}} + \frac{\left( {Q_{pvzf} - Q_{{Drain}\mspace{14mu} {Only}\mspace{14mu} {Measurement}\mspace{14mu} {Value}}} \right)}{\left( {C_{{{dQ}/{dT}}\; 0} + {C_{{{dQ}/{dT}}\; 1}P} + {C_{{{dQ}/{dT}}\; 2}/T_{zf}^{2}}} \right)}}} & (4)\end{matrix}$

Operation 215 updates the Tzf relationship for the test injector usingthe new Tzf value along with the prior Tzf relationship. In certainforms, operation 215 uses a Kalman Filter or similar adaptive process ortechnique to update the T_(zf) coefficients for the injector inaccordance with equation (5):

1/T _(zf) =C _(Tzf0) +C _(Tzf1) P+C _(Tzf2) /P  (5)

Operation 216 updates the relationship between the change in the drainquantity and the change in the commanded injector on-time for the testinjector. In certain forms, operation 216 updates Q_(pvzf) for theinjector in accordance with equation (6):

Update Q _(pvzf(injector)) =Q _(pvzf(nominal))+(Table values as afunction of Pressure)*(T _(zf(injector)) −T _(zf(nominal)))  (6)

In addition to the operations described above, an additional operationnot illustrated in FIG. 3 may be performed at engine production or afteran injector change service events which initialize the coefficientswhich define T_(zf) for each injector in accordance with equation (1).This initiation may utilize FON seeding based on end of life designdefinitions or empirical data.

With reference to FIG. 4, there is illustrated graph 400 depictingcertain aspects of the above-described process and modeling methodologyfor determining or estimating Q_(pvzf) and T_(zf) which includesoff-engine calibration and on-engine adaptation. In a first aspect,graph 400 illustrates test rig measurement values 401-408 for an exampleinjector which measured values of Q_(pvzf) at commanded values of T_(zf)at different pressures (300, 450, 700, 1000, 1200, 1500, 1800 and 2100bar, respectively). Test rig measurement values 401-408 may be providednon-adaptive, static values predetermined through off-engine calibrationof a particular type of injector or class of injectors and are thereforereasonable starting estimates of how any particular injector of thegiven type or class will perform, although each particular injector islikely to vary from such nominal performance. Graph 400 furtherillustrates curve 410 which has been determined from measurements401-408 by performing a curve fit operation in accordance with equation(1) such that curve 410 indicates commanded injector on-times which areintended to produce a drain flow only injection events.

In a second aspect, graph 400 illustrates on-line measurements 421-428for the example injector which measured values of Q_(pvzf) for commandedvalues of T_(zf) at different pressures (300, 450, 700, 1000, 1200,1500, 1800 and 2100 bar, respectively). The commanded on time values formeasurements 421-428 can be determined by calculating a safety marginbelow curve 410. In certain forms, the non-injection drain quantitymargin (Q_(non-injection drain quantity margin)) may be determined inaccordance with equation (7) which is used to define a relationshipbetween the change Qpvzf and the change in Tzf is shown in equation (7):

$\begin{matrix}{\frac{{dQ}_{{Drain}\mspace{14mu} {below}\mspace{14mu} T_{zf}}}{{dT}_{command}}-={C_{{{dQ}/{dT}}\; 0} + {C_{{{dQ}/{dT}}\; 1}P} + {C_{{{dQ}/{dT}}\; 2}/T_{zf}^{2}}}} & (7)\end{matrix}$

Equation (7) can be used in conjunction with aQ_(non-injection drain quantity margin) to calculate _(Tzf margin).Q_(non-injection drain quantity margin) can either be set as anon-adaptive valve as a function of pressure or it can adapt duringengine operation for each injector as a function of measurementvariability.

In each on-line measurement 421-428, the valve commanded on-timesincluding the Q_(non-injection drain quantity margin) (T_(zf margin))are commanded and the drain-only quantity(Q_(Drain Only Measured Value)) can be estimated from a measuredpressure change (□P) since it has been reasonably assured that noinjection will occur and the resulting pressure change thereforeindicates a drain-only quantity. From the drain-only quantities(Q_(Drain Only Measured Value)), the coefficients characterizinginjector performance can then be updated in accordance with equation (4)and the nominal test rig measurements values 401-408 can be updated andadapted based on the current actual operational performance of eachindividual injector. This technique allows substantially real-timeadjustments of the commanded values of T_(zf) which provide azero-injection reference from which desired injection can be determinedand injected.

With reference to FIG. 5 there is illustrated a graph 500 depictingcertain aspects of the adaption of Q_(pvzf) as a function of T_(zf) atdifferent pressures. For some injector configurations, as the commandedon-time required to initiate injection (T_(zf)) increases, theinjector's drain quantity (Q_(pvzf)) associated with that commandedon-time also increases. This trend in an increase in Q_(pvzf) as T_(zf)increases can be measured on an injector rig and input as a fixedrelationship in the calibration model. In the illustrated example, thedata indicates that at low pressures, Qpvzf tends to increase as Tzfincreases. At high pressure, Qpvzf tends to decrease as T_(zf)increases. Although the trend appears, there is significant variation inthis Qpvzf to T_(zf) relationship for individual injectors.

With reference to FIG. 6, there is illustrated a graph 600 depictingcertain aspects of the determination of an on-engine targeted drain flowquantity which provides a margin Q_(non-injection drain quantity margin)to limit the probability that an injection event will occur while alsominimizing the error in extrapolation between measurement zero-injectionvalues and non-zero-injection values. During on-engine injectoroperation, it is undesirable to produce unintended injection events.Accordingly, the margin Q_(non-injection drain quantity margin) isestablished so that the injector's targeted drain flow only injectionevents are at sufficient drain flow quantities below Q_(pvzf) to limitthe likelihood of any injection. However, in order to also reduce theerror in the drain flow quantity extrapolation, each injector's targeteddrain flow is offset by a margin that not too far below Q_(pvzf). Giventhat Q_(pvzf)−Q_(Drain Only Measurement Target) equates to a fixed tableas a function of pressure or an equation with coefficients which aredetermined from rig testing and do not adapt on-engine, the commandedon-time for the individual injector at the current system pressure maybe determined in accordance with equation (3). An alternative method atestablishing a real-time adaptive margin on-engine is to use themeasured variation in the measurements to establish the margin. Thesmaller the variation in the measurements, the smaller the margin.

As illustrated in graph 600 the resulting margin(Q_(non-injection drain quantity margin)) is illustrated as the offsetbetween nominal Q_(pvzf) curve 610 and the targeted measurement Q_(pvzf)curve 620 that provides targeted drain flow for on line measurement. Asillustrated in graph 600, the magnitude of the offset between curves 610and 620 varies with injection pressure. For example, because theillustrated example injector exhibits greater variance in when injectionoccurs at high pressure, as shown in FIG. 5, the offset is greater athigher pressure. Such variance over pressure is not necessarily limitedto a higher pressure effect and is properly determined empirically for agiven type or class of injectors as significant differences in thisvariance can be observed among these cohorts.

With reference to FIG. 7 there is illustrated a graph 700 depictingcertain aspects of a procedure for adaption of Q_(pvzf) as a function ofT_(zf). For some injector configurations, as the commanded on-timerequired to initiate injection [T_(zf)] increases, the injector's drainquantity [Q_(pvzf)] associated with that commanded on-time alsoincreases. This trend in an increase in Q_(pvzf) as T_(zf) increases canbe measured on an injector rig and input as a fixed relationship in thecalibration model. In the illustrated example, the sensitivity ofQ_(pvzf) to T_(zf) has the largest magnitude at low pressures. Therelationship of

$\frac{Q_{{pvzf}{({injector})}} - Q_{{pvzf}{({nominal})}}}{T_{{zf}{({injector})}} - T_{{zf}{({nominal})}}}$

can be predetermined in an off-engine calibration operation and providedin a non-adapting table or with non-adapting parameters which are afunction of pressure for each injector configuration and are obtainedbased on rig testing.

With reference to FIG. 8, there are illustrated graphs 810 and 820.Graph 810 depicts the results of nominal starting values for T_(zf)coefficients of C_(Tzf0) C_(Tzf), C_(Tzf2) which were determined for atype or class of injectors using the above-described off-enginecalibration operations. Graph 820 depicts the results of performing theabove above-described on-engine adjustment operations to adapt theT_(zf) coefficients of C_(Tzf0) C_(Tzf), C_(Tzf2) for an individualinjector based on is current operational characteristics.

It shall be appreciated that form of the method used to represent therelationships between Tzf and Qpvzf as a function of pressure can takemany forms based on the injector's configuration and operatingcharacteristics and the methodology shown in equations (1) through (7)is just one of many possible embodiments. For example, other embodimentsmay model this relationship in accordance with equation (8):

Qpvzf=C0+C1*P+C2/P+(Table values as a function of Pressure)*Tzf  (8)

As illustrated above, the measurement of pressure drops during zero-fuelinjection pulses provides a high degree of accuracy and precision. Suchmeasurement can be further enhanced through several techniques. Forexample, the signal to noise ratio (SNR) of pressure drop measurementscan be improved by determining a measured pressure value by averagingmultiple injection pulses. This averaging tends to average out andreduce the noise inherent in each measurement leading to an improvedSNR. On the other hand, measurements of multiple pulses presentadditional sources of error through the interaction between pulses thatare performed too closely together. Sufficient spacing of pulses in amulti-pulse measurement can mitigate the impact of inter-pulseinteraction. For one example injector, a pulse spacing of at least2.5-3.0 milliseconds was determined to provide sufficient mitigation ofinter-pulse interaction. The appropriate minimum pulse spacing may, ofcourse, vary for different injection systems although the generalprinciple of ensuring sufficient pulse spacing in multi-pulsemeasurements is applicable across a broad range of injector systems andscenarios. The particular spacing for a give injector type or class maybe determined, for example, by performing two-pulse measurements at avariety of pulse spacing and observing the magnitude of the effect onthe pressure measurement and estimate the magnitude of pilot valve drainfuel Qpvzf.

Another example technique which can be used to enhance accuracy andprecision of pressure drop measurements during zero-fuel injectionpulses can be realized by defining engine crank angle ranges mostsuitable for pulse measurement, whether single pulse or multi-pulsemeasurement. Injector fuel pumps are typically driven by one or more camlobes whose rotation is determined by engine crank angle. For example,with reference to FIG. 9, there is illustrated a graph 900 depicting anexample at an engine speed of 1200 rpm with a pump which pumps every 120engine degrees.

In graph 900 pumping event regions 910 occur approximately every 120degrees of engine crank angle. Pulse measurement in regions 910 shouldbe avoided to avoid error introduced by pumping pressure. Pre-pulseregions 920 and post-pulse regions 930 provide appropriate opportunitiesto measure injection pressure before and after zero fueling pulsecommands. Regions 940 define bands in which zero fueling pulse commandsmay be commanded while mitigating potential pumping error and allowingfor pre-pulse and post-pulse pressure measurements. For the engineconfiguration and the operating condition shown, regions 940 each offeran opportunity for up to four appropriately spaced multi-pulse drainevents to be commanded while still providing sufficient pre-pulse andpost-pulse pressure measurement windows and staying out of unintendedpumping regions.

The bandwidth of regions 940 and the corresponding number ofopportunities for appropriately spaced injection pulses varies fordifferent fuel pumps and also varies with engine speed. For example,with reference to FIG. 10, there is illustrated a graph 1000 depictingthe potential number of injection pressure measurements (drain pulses)per engine revolution as a function of engine speed. As shown in graph1000, the opportunity for multi-pulse measurements varies with thefrequency of pumping events. Thus, pumping every 240 degrees provides anincreased opportunity for multi-pulse measurements relative to pumpingevery 120 degrees. Graph 1000 also illustrates that multi-pulsemeasurements can be performed at most engine speeds, but tend to reducewith engine speed and may not be possible at engine speeds above acertain magnitude. This effect can be observed for both pumping every120 degrees and pumping every 240 degrees.

It shall be appreciated that various aspects of the present disclosuremay be implemented to provide a number of unanticipated benefitsincluding, without limitation, the following exemplary aspects. In oneaspect closed loop injected quantity fueling error may be minimized atall operating pressures in the zero and ultra-low fueling region. Inanother aspect, the intrusiveness of control measurements on engineoperation may be minimized. In a further aspect, undesired injectionquantities and frequency may be minimized. In an additional aspect,robustness of fuel injection controls may be maximized. It shall beappreciated that such minimization and maximization may includeimprovements constituting reductions or increases, respectively, oroptimizations and are not necessarily limited to an absolute ortheoretical minimization or maximization, although such results may beapproached or realized in certain embodiments. A further aspect providesprocessed data which can be directly utilized by a variety of lowfueling injector controls, which would occur to one of skill in the art,in order to minimize the closed loop ultra-low injected quantity fuelingerror at all operating pressures. Another aspect minimizes theintrusiveness on engine operation of injector measurement and injectioncontrol parameter adaption. For example, since no fuel is injected intothe cylinder, no engine permission is required to conduct eachmeasurement. In a further aspect, zero-injection pulses can be commandedat any timing relationship relative to the pump in order to minimize theprobability that self-pumping events corrupt the data. In anotheraspect, pulses can be commanded at any timing relationship relative tothe pump in order to more easily identify self-pumping events whichwould otherwise corrupt the data. In a further aspect, multiple pulsescan be commanded in each measurement window to improve the signal tonoise ratio. In another aspect, the accuracy and precision of theresults can be approximately 0.0±0.4 mg of error in the adaptedinjection control parameters. In a further aspect, pulses can becommanded prior to the measurement pulses in order to raise theinjector's drain pressure to its operational level. For injectorconfigurations in which the injected quantity is affected by theinjector's drain circuit pressure, commanding drain only pulses caneffectively precondition the drain circuit to the desired pressure levelprior to commanding subsequent on-times. For injectors that aresensitive to the drain circuit pressure, the magnitudes of the drainonly pulses can be used to diagnose and correct to injector draincircuit performance issues. For example, drain circuits may include acheck valve which is intended to act to maintain and regulate the draincircuit pressure. If the check valve leaks and fails to maintain thepressure, the drain circuit pressure would drop after injection eventsare terminated. If the relationship between the injectors drain onlyquantity and the drain circuit pressure is known for an injectorconfiguration based on prior rig or engine testing, this information canbe utilized real-time on-engine to characterize the operationalperformance of the drain circuit check valve and adapt to correct forits effect. In another aspect, data is obtained even when the injector'scharacteristics differ significantly from the nominal injector'scharacteristics. In a further aspect, the gain of the sum of theinjector's pilot valve drain flow and injected quantity flow relative tothe commanded on-time is lower at on-times less than Tzf than at on-timegreater than Tzf which improves the measurement accuracy. In anotheraspect, parameters which are dependent on the injector configuration andwhich do not adapt during engine operation can be relatively easilycalibrated from rig data. In a further aspect, the robustness of asystem pressure drop algorithm is improved. Since any removal of fluidfrom the pressurized volume reduces the system pressure, the multi-pulsedrain only pulse strategy detailed can be used to actively reduce thesystem pressure at any engine operating condition at which the currentsystem pressure is greater than the current system pressure. This activepressure reduction strategy can be used to simplify systems through theelimination of a separate active pressure reduction valve. Thismulti-pulse drain only pulse strategy could also be employed at engineshut down to reduce the system pressure. In another aspect, forcommanded on-times below on-times at which injection occurs, the drainquantity is independent of the cylinder pressure and differs frominjection producing commanded on-times which can be affected by thecylinder pressure. Parallel algorithms can be used to assist inestimating injection quantity interaction with the cylinder pressure. Ina further aspect, drain only pulses can be alternatively commanded on oroff for an injector even when another injector is operating and theresulting delta can be used to estimate the critical on-time. It shallbe further appreciated that the foregoing aspects may or may not beincluded in a given embodiment.

Aspects of certain example embodiments shall now be further described. Afirst example embodiment is a method of controlling an engine system,the method comprising: controlling a fuel injector to perform azero-fueling injector operation during operation of the engine, thezero-fueling injector operation including a non-zero injector on-timeresulting in zero fueling by the injector; determining an injectionsystem pressure change associated with the zero-fueling injectoroperation; modifying at least one fuel injection control parameter inresponse to the injection system pressure change; and using the modifiedfuel injection control parameter to control injection of fuel by thefuel injector during operation of the engine.

In certain forms of the first example embodiment, the at least oneinjection system pressure change comprises a fuel rail pressure change.In certain forms, at least one fuel injection control parametercomprises a maximum injector on-time which will produce zero fueling ata given injection system pressure. In certain forms, a plurality ofinstances of the acts of controlling, determining, and modifying areperformed separately for each of a plurality of fuel injectors. Incertain forms, the acts of controlling, determining, and modifying areperformed repeatedly during operation of the engine effective to adaptthe at least one fuel injection control parameter to changes in theperformance of the fuel injector. In certain forms, the act ofcontrolling the fuel injector is repeated multiple times for each act ofdetermining the at least one injection system pressure change. Incertain forms, the act of determining the at least one injection systempressure change comprises: performing a first injection system pressuremeasurement after a first engine crank angle range defining a first fuelpumping event and before a second engine crank angle range in which theact of controlling the fuel injector is performed, and performing asecond injection system pressure measurement after the second enginecrank angle range and before a third engine crank angle range defining asecond fuel pumping event. In certain forms, the act of modifying atleast one fuel injection control parameter comprises modifying one ormore coefficients of a model defining the maximum injector on-time. Incertain forms, the model defining the maximum injector on-time includesat least a first coefficient of a first term which is independent ofinjection system pressure and a second coefficient of a second termwhich is dependent on injection system pressure. In certain forms, theengine system is operated to propel a vehicle. Certain forms of thefirst example embodiment include the features of any two or more of theforegoing forms.

A second example embodiment is a system comprising: an engine; a fuelinjection system including a fuel injector; and an electronic controlsystem configured to perform the acts of: controlling the fuel injectorto perform a zero-fueling injector operation during operation of theengine, the zero-fueling injector operation including a non-zeroinjector on-time resulting in zero fueling by the injector; determiningan injection system pressure change associated with the zero-fuelinginjector operation; modifying at least one fuel injection controlparameter in response to the injection system pressure change; and usingthe modified fuel injection control parameter to control injection offuel by the fuel injector during operation of the engine.

In certain forms of the second example embodiment, the at least oneinjection system pressure change comprises a fuel rail pressure change.In certain forms, the at least one fuel injection control parametercomprises a maximum injector on-time which will produce zero fueling ata given injection system pressure. In certain forms, the fuel injectionsystem includes a plurality of injectors and the electronic controlsystem is configured to perform the acts of controlling, determining,and modifying separately for each of the plurality of fuel injectors. Incertain forms, the electronic control system is configured to performacts of controlling, determining, and modifying repeatedly duringoperation of the engine effective to adapt the at least one fuelinjection control parameter to changes in the performance of the fuelinjector. In certain forms, the electronic control system is configuredto perform the act of controlling the fuel injector multiple times foreach act of determining the at least one injection system pressurechange. In certain forms, the electronic control system is configured toperform the act of determining the at least one injection systempressure by: performing a first injection system pressure measurementafter a first engine crank angle range defining a first fuel pumpingevent and before a second engine crank angle range in which the act ofcontrolling the fuel injector is performed, and performing a secondinjection system pressure measurement after the second engine crankangle range and before a third engine crank angle range defining asecond fuel pumping event. In certain forms, the electronic controlsystem is configured to perform the act of modifying at least one fuelinjection control parameter by modifying one or more coefficients of amodel defining the maximum injector on-time. In certain forms, the modeldefining the maximum injector on-time includes at least a firstcoefficient of a first term which is independent of injection systempressure and a second coefficient of a second term which is dependent oninjection system pressure. In certain forms, the engine system isconfigured as a prime mover of a vehicle. Certain forms of the secondexample embodiment include the features of any two or more of theforegoing forms.

A third example embodiment is an apparatus for controlling operation ofan engine system including a fuel injection system including at leastone fuel injector, the apparatus comprising a non-transitorycontroller-readable memory medium storing instructions executable by acontroller to the acts of: commanding the fuel injector to perform azero-fueling injector operation during operation of the engine, thezero-fueling injector operation including a non-zero injector on-timeresulting in zero fueling by the injector; determining an injectionsystem pressure change associated with the zero-fueling injectoroperation; modifying at least one fuel injection control parameter inresponse to the injection system pressure change; and using the modifiedfuel injection control parameter to control injection of fuel by thefuel injector during operation of the engine.

In certain forms of the third example embodiment, the at least oneinjection system pressure change comprises a fuel rail pressure change.In certain forms, the at least one fuel injection control parametercomprises a maximum injector on-time which will produce zero fueling ata given injection system pressure. In certain forms, the fuel injectionsystem includes a plurality of injectors and the electronic controlsystem is configured to perform the acts of commanding, determining, andmodifying are performed separately for each of the plurality of fuelinjectors. In certain forms, the electronic control system is configuredto perform acts of commanding, determining, and modifying repeatedlyduring operation of the engine effective to adapt the at least one fuelinjection control parameter to changes in the performance of the fuelinjector. In certain forms, the electronic control system is configuredto perform the act of commanding the fuel injector multiple times foreach act of determining the at least one injection system pressurechange. In certain forms, the electronic control system is configured toperform the act of determining the at least one injection systempressure by: performing a first injection system pressure measurementafter a first engine crank angle range defining a first fuel pumpingevent and before a second engine crank angle range in which the act ofcommanding the fuel injector is performed, and performing a secondinjection system pressure measurement after the second engine crankangle range and before a third engine crank angle range defining asecond fuel pumping event. In certain forms, the electronic controlsystem is configured to perform the act of modifying at least one fuelinjection control parameter by modifying one or more coefficients of amodel defining the maximum injector on-time. In certain forms, the modeldefining the maximum injector on-time includes at least a firstcoefficient of a first term which is independent of injection systempressure and a second coefficient of a second term which is dependent oninjection system pressure. Certain forms of the third example embodimentinclude the features of any two or more of the foregoing forms.

A fourth example embodiment is a method of adapting fuel injection tocurrent on-engine injector operational characteristics, the methodcomprising: controlling an injector to perform one or more injectionactuations resulting in zero engine fueling; monitoring one or moreinjection system pressure responses to the one or more injectoroperations; adapting one or more fuel injection control parameters inresponse to the one or more injection system pressure responses; andcommanding drain only pulses in response to the one or more adapted fuelinjection control parameters.

In certain forms of the fourth example embodiment, the act of adaptingone or more fuel injection control parameters includes modifying one ormore coefficients of a model defining a maximum injector on-time thatwill result in zero fueling.

In certain forms of the fourth example embodiment, the act of adaptingone or more fuel injection control parameters includes modifying one ormore coefficients of a model defining a maximum injector on-time thatwill result in zero fueling, wherein the model defining the maximuminjector on-time includes at least a first coefficient of a first termwhich is independent of injection system pressure and a secondcoefficient of a second term which is dependent on injection systempressure.

In certain forms of the fourth example embodiment, the act of adaptingone or more fuel injection control parameters includes modifying one ormore coefficients of a model defining a maximum injector on-time thatwill result in zero fueling, wherein the model defining the maximuminjector on-time includes at least a first coefficient of a first termwhich is independent of injection system pressure and a secondcoefficient of a second term which is dependent on injection systempressure, where the model is configured to update coefficients of theequation:

${\frac{1}{T_{zf}} = {C_{{Tzf}\; 0} + {C_{{Tzf}\; 1}P} + \frac{C_{{Tzf}\; 2}}{P}}},$

wherein T_(zf) is the maximum injector on time, P is pressure, andC_(Tzf0) C_(Tzf1), C_(Tzf2) are nominal starting coefficient valueswhich are determined by off-engine testing.

In certain forms of the fourth example embodiment, the act of adaptingone or more fuel injection control parameters includes modifying one ormore coefficients of a model defining a pilot valve drain quantityassociated with a maximum injector on-time that will result in zerofueling.

In certain forms of the fourth example embodiment, the act of adaptingone or more fuel injection control parameters includes modifying one ormore coefficients of a model defining a pilot valve drain quantityassociated with a maximum injector on-time that will result in zerofueling, wherein the model is configured to update coefficients of theequation:Q_(pvzf)=C_(Qpv_nominal_0)+C_(Qpv_nominal_1)*P+C_(Qpv_nominal_2)*P²,wherein Q_(pvzf) is the pilot valve drain quantity associated with amaximum injector on-time that will result in zero fueling, P ispressure, and C_(Qpv_nominal_0), C_(Qpv_nominal_1), C_(Qpv_nominal_2)are nominal starting coefficient values which are determined byoff-engine testing.

While illustrative embodiments of the disclosure have been illustratedand described in detail in the drawings and foregoing description, thesame is to be considered as illustrative and not restrictive incharacter, it being understood that only certain exemplary embodimentshave been shown and described and that all changes and modificationsthat come within the spirit of the claimed inventions are desired to beprotected. It should be understood that while the use of words such aspreferable, preferably, preferred or more preferred utilized in thedescription above indicates that the feature so described may be moredesirable, it nonetheless may not be necessary and embodiments lackingthe same may be contemplated as within the scope of the invention, thescope being defined by the claims that follow. In reading the claims, itis intended that when words such as “a,” “an,” “at least one,” or “atleast one portion” are used there is no intention to limit the claim toonly one item unless specifically stated to the contrary in the claim.When the language “at least a portion” and/or “a portion” is used theitem can include a portion and/or the entire item unless specificallystated to the contrary.

1. A method of controlling an engine system, the method comprising:controlling a fuel injector to perform a zero-fueling injector operationduring operation of the engine, the zero-fueling injector operationincluding a non-zero injector on-time resulting in zero fueling by theinjector; determining an injection system pressure change associatedwith the zero-fueling injector operation; modifying at least one fuelinjection control parameter in response to the injection system pressurechange; and using the modified fuel injection control parameter tocontrol injection of fuel by the fuel injector during operation of theengine.
 2. The method of claim 1 wherein the at least one injectionsystem pressure change comprises a fuel rail pressure change.
 3. Themethod of claim 1 wherein the at least one fuel injection controlparameter comprises a maximum injector on-time which will produce zerofueling at a given injection system pressure.
 4. The method of claim 1wherein a plurality of instances of the acts of controlling,determining, and modifying are performed separately for each of aplurality of fuel injectors.
 5. The method of any of claim 1 wherein theacts of controlling, determining, and modifying are performed repeatedlyduring operation of the engine effective to adapt the at least one fuelinjection control parameter to changes in the performance of the fuelinjector.
 6. The method of claim 1 wherein the act of controlling thefuel injector is repeated multiple times for each act of determining theat least one injection system pressure change.
 7. The method of claim 1wherein the act of determining the at least one injection systempressure change comprises: performing a first injection system pressuremeasurement after a first engine crank angle range defining a first fuelpumping event and before a second engine crank angle range in which theact of controlling the fuel injector is performed, and performing asecond injection system pressure measurement after the second enginecrank angle range and before a third engine crank angle range defining asecond fuel pumping event.
 8. The method of claim 3 wherein the act ofmodifying at least one fuel injection control parameter comprisesmodifying one or more coefficients of a model defining the maximuminjector on-time.
 9. The method of claim 8 wherein the model definingthe maximum injector on-time includes at least a first coefficient of afirst term which is independent of injection system pressure and asecond coefficient of a second term which is dependent on injectionsystem pressure.
 10. The method of claim 1 wherein the engine system isoperated to propel a vehicle.
 11. A system comprising: an engine; a fuelinjection system including a fuel injector; and an electronic controlsystem configured to perform the acts of: controlling the fuel injectorto perform a zero-fueling injector operation during operation of theengine, the zero-fueling injector operation including a non-zeroinjector on-time resulting in zero fueling by the injector, determiningan injection system pressure change associated with the zero-fuelinginjector operation, modifying at least one fuel injection controlparameter in response to the injection system pressure change, and usingthe modified fuel injection control parameter to control injection offuel by the fuel injector during operation of the engine.
 12. The systemof claim 11 wherein the at least one injection system pressure changecomprises a fuel rail pressure change.
 13. The system of claim 11wherein the at least one fuel injection control parameter comprises amaximum injector on-time which will produce zero fueling at a giveninjection system pressure.
 14. The system of claim 11 wherein the fuelinjection system includes a plurality of injectors and the electroniccontrol system is configured to perform the acts of controlling,determining, and modifying separately for each of the plurality of fuelinjectors.
 15. The system of claim 11 wherein the electronic controlsystem is configured to perform acts of controlling, determining, andmodifying repeatedly during operation of the engine effective to adaptthe at least one fuel injection control parameter to changes in theperformance of the fuel injector.
 16. The system of claim 11 wherein theelectronic control system is configured to perform the act ofcontrolling the fuel injector multiple times for each act of determiningthe at least one injection system pressure change.
 17. The system ofclaim 11 wherein the electronic control system is configured to performthe act of determining the at least one injection system pressure by:performing a first injection system pressure measurement after a firstengine crank angle range defining a first fuel pumping event and beforea second engine crank angle range in which the act of controlling thefuel injector is performed, and performing a second injection systempressure measurement after the second engine crank angle range andbefore a third engine crank angle range defining a second fuel pumpingevent.
 18. The system of claim 13 wherein the electronic control systemis configured to perform the act of modifying at least one fuelinjection control parameter by modifying one or more coefficients of amodel defining the maximum injector on-time.
 19. The system of claim 18wherein the model defining the maximum injector on-time includes atleast a first coefficient of a first term which is independent ofinjection system pressure and a second coefficient of a second termwhich is dependent on injection system pressure.
 20. The system of claim11 wherein the engine system is configured as a prime mover of avehicle. 21.-29. (canceled)
 30. A method of adapting fuel injection tocurrent on-engine injector operational characteristics, the methodcomprising: controlling an injector to perform one or more injectionactuations resulting in zero engine fueling; monitoring one or moreinjection system pressure responses to the one or more injectoroperations; adapting one or more fuel injection control parameters inresponse to the one or more injection system pressure responses; andcommanding drain only pulses in response to the one or more adapted fuelinjection control parameters.
 31. The method of claim 1 wherein the actof adapting one or more fuel injection control parameters includesmodifying one or more coefficients of a model defining a maximuminjector on-time that will result in zero fueling.
 32. The method ofclaim 31 wherein the model defining the maximum injector on-timeincludes at least a first coefficient of a first term which isindependent of injection system pressure and a second coefficient of asecond term which is dependent on injection system pressure.
 33. Themethod of claim 32 where the model is configured to update coefficientsof the equation:${\frac{1}{T_{zf}} = {C_{{Tzf}\; 0} + {C_{{Tzf}\; 1}P} + \frac{C_{{Tzf}\; 2}}{P}}},$wherein T_(zf) is the maximum injector on time, P is pressure, andC_(Tzf0), C_(Tzf1), C_(Tzf2) are nominal starting coefficient valueswhich are determined by off-engine testing.
 34. The method of claim 1wherein the act of adapting one or more fuel injection controlparameters includes modifying one or more coefficients of a modeldefining a pilot valve drain quantity associated with a maximum injectoron-time that will result in zero fueling.
 35. The method of claim 34where the model is configured to update coefficients of the equation:Q_(pvzf)=C_(Qpv_nominal_0)+C_(Qpv_nominal_1)*P+C_(Qpv_nominal_2)*P²,wherein Q_(pvzf) is the pilot valve drain quantity associated with amaximum injector on-time that will result in zero fueling, P ispressure, and C_(Qpv_nominal_0), C_(Qpv_nominal_1), C_(Qpv_nominal_2)are nominal starting coefficient values which are determined byoff-engine testing.